RU2245216C1 - Method for making double-layer rolling rolls - Google Patents

Abstract

FIELD: metallurgy, possibly manufacture of double -layer rolling rolls.

SUBSTANCE: method comprises steps of casting outer layer of roll in the form of hollow cylinder by squeezing at crystallization under pressure and placing it into casting mold; before placing cylinder into casting mold covering it from inside with thermosetting composition and from outside - with refractory pickup prevention composition; after placing cylinder into casting mold, pouring it along outer surface with sand; casting metal of core part and of journals.

EFFECT: high-strength joint of working layer with metal of central part, lowered volume of mechanical working of roll barrel due to producing accurate-size castings.

4 cl

Description

The invention relates to the field of metallurgy n can be used in rolling production.

A known method of manufacturing a two-layer rolling rolls, including casting the core of the roll and subsequent casting of the outer layer (S.Ya. Golovin “Special types of casting”, Mashgiz, 1955, p. 239).

The method has not received distribution due to the complexity of the process.

A known method of producing two-layer rolls by manufacturing a core followed by electroslag surfacing with liquid metal of the outer working layer, including from high-speed steel (Information leaflet of NKMZ, Kramatorsk, Donetsk region, Ukraine, 2002).

The method is energy-intensive and low-efficient, requires cumbersome expensive equipment.

Closest to the claimed technical solution adopted for the prototype can be attributed to a method of manufacturing a two-layer rolling rolls, including the casting of the outer working layer, the installation of the resulting hollow cylinder in the mold and subsequent pouring into the metal form of the core and the neck of the roll with preheating of the cylinder by electric current (C .Ya. Golovin “Special types of casting”, Mashgiz, 1955, p. 239).

The disadvantages of the method include:

- frequent peeling of the outer layer from the core due to the non-welding of bimetals;

- technological complexity of the process due to the need for electric heating;

- limited technological capabilities in the manufacture of rolls with cast streams, as well as bimetals such as high-chromium cast iron, steel (soft cast iron), high-speed steel - carbon steel (high-strength cast iron), white cast iron of the outer working layer with a profiled surface - soft cast iron (high-strength cast iron);

- a large amount of machining of difficult to process material.

The aim of the invention is to eliminate the noted drawbacks, namely the elimination of peeling of the outer layer of the roll from the core, the elimination of its electrical heating in the mold, the expansion of technological capabilities through the use of highly wear-resistant materials and accurate castings, including with a profiled work surface, reducing the amount of machining of difficult materials.

The problem is solved due to the fact that in the method of manufacturing two-layer rolling rolls, including the casting of the outer working layer, the installation of the resulting hollow cylinder in the casting mold and subsequent pouring into the metal mold of the core of the roll necks, casting of the outer roll layer is obtained by squeezing with crystallization under pressure (LVKD), the cast hollow cylinder before being installed in the mold is coated inside with a thermosetting composition, and outside with a refractory non-stick composition and the last f installing it in a mold on the outer surface with sand. At the same time, wear-resistant materials such as high-chromium cast iron are used as the material of the outer working layer of the roll.

To obtain casting of the outer working layer of the roll, use its gasified polystyrene foam model with a profiled or even outer surface and a profiled (“developed”) inner surface.

Accepted techniques provide:

- due to injection molding using the HDLC method using the polystyrene foam model, obtaining an accurate cast billet of the outer working layer of the roll with fine primary grain, including with cast brooks made of wear-resistant materials, reducing the amount of machining;

- due to the thermosetting coating available on the inner “developed” surface of the casting of the outer working layer of the roll, thermal insulation (“sand”) on its outer surface, obtaining a strong connection of bimetals and eliminating delamination;

- obtaining rolls of increased wear resistance in a more economical than known way.

The method is as follows.

To obtain a roll with a profiled working surface of the barrel, a polystyrene foam model of the hollow cylinder of the outer working layer of the roll is made with the geometry of the inner surface repeating the geometry of the outer surface, the model is coated with refractory paint and placed in a container of the casting machine by squeezing with crystallization under pressure (LVCD).

The 30Kh32N3FL melt is poured into the squeezing chamber and, at a temperature of 1300-1320 ° C (in the crystallization interval), it is squeezed into the working cavity of the container, burning a polystyrene foam model with a vacuum applied.

After the polystyrene foam is replaced by a molten metal, a gas pressure of 5 atm is supplied to the container and held until the casting solidifies completely, after which a knockout is performed.

The sprues and profits are cut from the finished casting, they clean the inner and outer surfaces, they are heated to 200 ° C and the thermite mixture powder is applied to the inner surface, and a refractory heat-insulating coating, for example, zirconium oxide, is applied to the outer surface.

None of the vertically arranged sand molds for forming the roll neck establishes the prepared casting of the hollow cylinder of the outer working layer, covers the outside with dry quartz sand to the wall of the outer shell (flask), sets the upper mold on the cylinder to form another roll neck and profit.

Carbon steel or high-strength cast iron is poured into the assembled form with overheating of the liquidus temperature, which ensures the heating of the hollow cylinder, the thermochemical reaction on its inner surface and the welding of bimetals. At the same time, during pouring and solidification of the melt, a strong mechanical connection of the outer cylinder and the core occurs due to the complex geometry of the inner surface of the cylinder.

After cooling, the casting is knocked out, heat treated (if necessary), shot blasting and the process is repeated.

The use of the invention allows to obtain rolling rolls of increased wear resistance at lower cost than in the known methods, to obtain bimetallic rolls with cast streams, to obtain a strong connection of the working layer with the core metal, to increase the reliability of bimetallic rolls, to reduce the volume of machining of the roll barrel by obtaining a workpiece with precise the dimensions.

Claims (4)

1. A method of manufacturing a two-layer rolling rolls, including casting the outer working layer of the roll in the form of a hollow cylinder, installing it in a mold, pouring the core and the neck of the roll into metal form, characterized in that the hollow cylinder is cast by squeezing with crystallization under pressure, before installation the cylinder in the mold is coated on the inside with a thermosetting composition, and on the outside with a refractory non-stick composition, after installing the cylinder in the mold, fill it with sand on the outer surface. 2. The method according to claim 1, characterized in that the outer working layer is cast from high chromium cast iron. 3. The method according to claim 1, characterized in that the outer working layer is cast from high speed steel. 4. The method according to claim 1, characterized in that the casting of the outer working layer is carried out using a gasified polystyrene foam model with a profiled or even outer surface and a profiled inner surface.